ORIGINAL: Rafeek
Andreas,
You are under powered, but if u wish to stick with the engine u have u gotta balance without the addition of so much weight. Although moving the engine forward might sound drastic its worth a try IMHO. My guess is that if you move it forward by placing a piece of mdf board or plywood behind the engine mount you may end up adding 250 gm only.
Rafeek
Facia,
If it flys good don't worry about adding weight. It's a cub. The emphasis on on never adding weight has its place - but it's a Sunday flyer for gosh sakes.
John